Viscoelastic properties of dilute macromolecular solutions can provide information about molecular size, shape, and flexibility, and polymerization of subunits. The Birnboim-Schrag multiple-lumped resonator will be used to study, at very low concentrations, fibrinogen, intermediate fibrin polymers, and other biomacromolecules such as tropomyosin, tropocollagen, tobacco mosaic virus, polyamino acids, and hyaluronic acid, in the frequency range from 100 to 8000 Hz. The frequency dependence of the storage and loss shear moduli will be related to features such as partial flexibility of long helical structures, deformability of corpuscular proteins, and aspects of helix- coli transitions. Studies of the first stage of polymerization of fibrin, and of the elastic and viscoelastic properties of fibrin clots, will be related to the secondary forces holding the fibrin units together in the absence of ligation and the primary bonds introduced when ligation is effected. Measurements of creep and stress relaxation will be made on clots with and without ligation, with varying coarseness of structure, formed by thrombin and other enzymes capable of activating polymerization, as well as by polymerization of fibrin monomer induced by pH change. Bibliographic references: "Infinite-Dilution Viscoelastic Properties of Tobacco Mosaic Virus", by N. Nemoto, J.L. Schrag, J.D. Ferry, and R.W. Fulton, Biopolymers, 14,409-417 (1975); "Inifinite- Dilution Viscoelastic Properties of Poly(n-hexyl isocyanate)", by N. Nemoto, J. S. Schrag, and J.D. Ferry, Polymer J., 7, 195-201 (1975).